Another Empress Wave theory

[EvilDrGanymede]

Originally posted by TheEngineer:
Doesn´t that also mean, that any large objects (main stars, gas giants) especially in the departure star system may block quite a angle segment of possible destination jump vectors
(if you are near to that 100D limit) ?

Take a G2 V companion star (like the sun) orbiting a G2 V primary at 10 AU. And assume there's an earthlike planet that you're jumping from around the primary at a distance of 1 AU. Assuming the planet is between the primary and the companion, the companion star itself will subtend an angle of about 3.5 minutes of arc in the planet's sky (that's for the diameter of the star), and its 100D limit (0.93 AU) will subtend an angle of 5.75 degrees (assuming I've done the maths right!). Doesn't exactly block off a huge chunk of sky, but it could be a bit inconvenient - though the chances that your destination star in within that 100D limit are rather low.

A bigger problem in this case is if your destination star is blocked by the 100D limit of the PRIMARY. The 100D 'sphere' blots out a good 52 degrees or so of sky, so you'd have to do a heck of a lot of maneuvering to get to a point in space that you can jump from in order to see your destination star outside of that 'shadow'.

 

[kaladorn]

I'll tell you what I want, Citizen Thrash. A translation of the contents of that link into English. It is undoubtedly mathematically involved, but how about it.

That is to say:

I have two systems, Alpha and Beta, I wish to transit between.

Alpha Primary's 100D limit extends some distance. It therefore cuts some chunk of the sky out of the picture. But Alpha also has say 10 other planets, two of which are gas giants and one asteroid/planetoid belt. Do these not factor in by blocking out some chunk of space?

(Note, I confine my question to two dimensions, as space in the TU is 2D... the masking risk drops a bit in a 3 space context where a short trip out of the plane will free you from many obstructions).

The Beta has a Primary. If we want to be really interesting, it has a Companion too. Maybe the mainworld is in a planetoid belt or maybe it is the moon of a gas giant. In any event, there is some chance the planet will be on the opposite side of Beta's sun from where you want it, thus forcing you to jump.... further out. And fly in to your destination. And Beta, of course, has a number of other inner and outer worlds which could line up and interfere.

You've got lots of fancy math on that page but what I really want to know is just this:

1) Does the analysis you've done consider:
- binary and trinary systems
- mainworlds inside a 100D limit of the primary at either end
- the other N worlds in each system

If not, is that because an analysis revealed they really wouldn't matter? Or just for simplification?

If the analysis does include them, what impact do they actually have?

And can you summarize in plain english without resorting to too much fancy math. Ster-radians etc. notwithstanding.... it has been a few years since I took highschool trigenometry/geometry.

That is all I want. It doesn't have to have all the math, just some analysis of the math that was involved....

 

[TheEngineer]

Hi Thrash,

sorry, I just missed to step into your link in detail. My fault.

Do you think the numbers and propabilities presented in the post will remain constant, even if everything is moving ?

Regards,

Mert

 

[Andrew Boulton]

we've been told the OTU answer

I don't know if anybody knows what the OTU is anymore. This change appeared in GT, but GT has already diverged from established history by killing Dulinor instead of Strephon, so what's reality?

 

[Andrew Boulton]

The opponents of jump masking (specifically Hans Rancke-Madsen, if I recall correctly) coined the term "jump shadowing" for the alternate approach, which I defined above (i.e., "only entry and intended breakout points are affected by 100D limits").

Riiight. So, jump shadowing is established reality as presented in CT, MT, TNE, T4 (and T20?), and jump masking is the alternate GT method. I'm not quite sure where the shadow bit comes in.

 

[Andrew Boulton]

So in one case, the first object affects the jump; in the second, it doesn't. What happens on the boundary between the two cases?

Either there's a space between the 100d zones (in which case you re-enter there), or there isn't (in which case they act as a single object).

Something else just occurred to me: if you're kicked out when you hit any 100d zone, then it's no longer possible to jump from within 100d.

 

[Andrew Boulton]

The question of whether intervening objects affect jump was never resolved

Prior to GT:FT, there was never any suggestion that they did. Since it's a fairly important point, the fact that the rules never even mentioned it once in four sets of rules over 20 years could only mean that they don't.

 

[TheEngineer]

Hi,

I have to agree with Andrew.
There really was enough time to establish any ruleset dealing with this important question.

It would be a bit strange to to create such new "facts" now , especially because of the impact on the TU.

Regards,

Mert

 

[Andrew Boulton]

I guess the discontinuity between these doesn't bother you the way it does me.

Either there's a space, or there isn't. Either you're trying to jump into a 100d zone, or you're not.

The ability to jump outbound from less than 100D (with appropriate hazards) is part of the definition of jump

But so, apparently, is the inibility to cross any part of any 100d zone along the way. You can't have it both ways. Either they all cause...err...premature ejaculation...or they don't.

If they do, then you clearly can't jump from within 100d.

 

[Andrew Boulton]

Mr. Miller's 1985 "Jumpspace" article could be (and was) interpreted just as he apparently intended it

Sadly, only by him. It's ambiguous at best. You *could* interpret it that way, but only if you had some other reason to believe that's how it works.

Absence of evidence is not evidence of absence.

If the rules don't tell us something is true - and, in fact, imply the opposite is true - how are we supposed to know?

You have still failed to explain why the effects of permanently masked worlds (those within the 100D limits of their primaries at all times) were never mentioned, either.

Short answer: simplicity (but I'm surprised to hear that the rules never mentioned it - it was certainly known about and discussed).

Long answer: because the required information isn't always available. At a minimum you need to know the stellar type and the orbit number of the mainworld. The former didn't start to become available until late CT/early MT, and the latter requires you to actually generate the system. It's easier to just ignore the problem.

I just have no trouble finding situations that are permeable in one direction, but not in its opposite.

So jump masking has now gone from "Thou shalt not cross 100d" to "well, okay, you can sometimes".

 

[EvilDrGanymede]

Originally posted by Andrew Boulton:
If the rules don't tell us something is true - and, in fact, imply the opposite is true - how are we supposed to know?

I'm not seeing where they're implying an opposite here. This has been canonical since 1985 at least-I don't know why it's not been explicitly explained in anything else before GT, but that doesn't mean it wasn't there.

So jump masking has now gone from "Thou shalt not cross 100d" to "well, okay, you can sometimes"

It's not gone from one to the other - it's always said that. The 'slope' analogy is quite a good one - you can jump from within 100D but you'd be more likely to misjump, but you can't aim to arrive within 100D because you'll always be dumped out at the 100D distance. It doesn't have to be symmetrical. Surely this isn't so hard to grasp?

 

[Andrew Boulton]

I'm not seeing where they're implying an opposite here.

By omission. If intervening matter was significant, the rules would say so. They don't, therefore there's no reason to believe it is. The *only* places where 100d limits are mentioned in either the rules or Marc's article are at the start and destination points, therefore those are the only places where we have any reason to believe they matter.

I don't know why it's not been explicitly explained in anything else before GT

CT was very clearly and concisely written, there are very few ambiguities. There've also been plenty of opportunities to clarify it - 2nd ed LBB, JTAS, MT, Challenge, TNE, T4. And yet not once in 20 years did he ever mention it. The only logical conclusion is that it's a change.

but that doesn't mean it wasn't there.

Clearly it does, otherwise we would've noticed it.

 

[kaladorn]

Originally posted by thrash:
No, only perhaps that you can't jump further into the 100D zone. The ability to jump outbound from less than 100D (with appropriate hazards) is part of the definition of jump, along with precipitating out at 100D inbound.

Nice tap shoes, Chris.

But how about this:

I'm inside 2 100D limits simultaneously, but in a situation where (if I strictly followed what you just said above), I am jumping away from the stronger of the two fields, even though I am jumping towards the other. Hence I'm actually jumping 'out' of the stronger influence's 100D zone (and the net influence is less) while actually jumping *towards* or *deeper into* the other 100D zone.

Still, I admit that is the only situaiton I can see this being a problematic rendering of the context.

 

[EvilDrGanymede]

Originally posted by Andrew Boulton:
By omission. If intervening matter was significant, the rules would say so. They don't, therefore there's no reason to believe it is. The *only* places where 100d limits are mentioned in either the rules or Marc's article are at the start and destination points, therefore those are the only places where we have any reason to believe they matter.

I can see why one would think that, certainly. But I thought MWM clarified that for Christopher Thrash? If he did, that's what goes in the OTU, whether we like it or not.

Here's what he said (quote from Chris' post on page 5):

In writing GURPS Traveller: Far Trader, it became important to know whether this was really what Mr. Miller meant -- that a world or large object anywhere along the jump line causes precipitation, rather than just at the intended breakout point -- or whether we needed to use some other version and make a correction to GT. In fact, the farport debate was one of the critical issues decided upon this interpretation. I wrote to Mr. Miller for his ruling, and this was his response:

"1. A ship IS precipitated out of jump when it crosses the 100D line from any object (which is greater than that of the ship).

"Restrictions. Jump cannot take place within 100 diameters of body (star, gas giant, world, planetoid, or even another ship) larger than itself.
"If a plotted course intersects a 100 diameter sphere around any object larger than the ship, the ship is "precipitated out" of jump space.
"In System Jumps. It is possible to jump within a star system: The jump still takes a week (168 hours or so). In some cases, the jump is more efficient than using maneuver drive.

"2. SO, if you plot a jump in a straight line from here to there, and between here and there there happens to be an object of sufficient size, then you aren't going to go all the way. You'll precipitate out of jump when you hit the 100D limit.

"3. It is based on D rather than mass. Take that as an article of faith. We are talking about an object with some appreciable densitry however, so most gas clouds don't apply. If essence, the object must be a star or a world or a solid object ratehr than a nebula or comet tail.

"4. Sometimes there is an uncharted or unexpected thing in the way (big ship, planetoid, whatever. That would make you precipitate out. BTW, this implies that there is a one-to-one mapping between jump space and real space."

Marc W. Miller, private correspondence, 28 December 1998.

That sounds fairly unambiguous to me, and that's what GT followed.

 

[kaladorn]

Andrew,

You can attach the word 'logical' to your reasoning, but you might want to be a bit careful, lest the world 'fallacy' also be appended....

The absence of an explanation of something does not, de facto or de jure, provide any implication about that thing that you do not personally chose to take.

 

[TheEngineer]

Hi Travellers,

I guess we're getting into a difficult point of discussion.
Before we start another canonical war I would like to ask what kind of value one or the other method has for gameplay ?

And I would like to ask for the gameplay impact of the masking stuff on the TU beyond a minor travel time delay.

Once I had a setting in Glisten, quite a large Belt in the Marches. Referring to the masking effect large regions would be effectivly inaccessible (at least in an economical way).

I really would like to now how this part is managed by the folks playing Traveller.
Perhaps one should make a poll.

Well, its late..

regards,

Mert

 

[EvilDrGanymede]

Originally posted by thrash:
</font><blockquote>quote:</font><hr />Originally posted by kaladorn:
I'm inside 2 100D limits simultaneously, but in a situation where (if I strictly followed what you just said above), I am jumping away from the stronger of the two fields, even though I am jumping towards the other. Hence I'm actually jumping 'out' of the stronger influence's 100D zone (and the net influence is less) while actually jumping *towards* or *deeper into* the other 100D zone.

Personally, I wouldn't allow a jump from, say, a point at 90D to one at 15D away from a single object at all.
</font>[/QUOTE]I think I'd say that it's impossible since there isn't a valid mathematical solution to the jump, so you can't plot the destination point. The jump solution would involve singularities or negative numbers or somesuch.

Even if it was possible though, the ship has a significant chance of misjump by leaving within the 100D limit, and assuming it did make the jump and didn't get lobbed 30 parsecs in a random direction or destroyed, I think the best (ie least painful) thing that could happen would be that it'd be shunted to the edge of one of the two 100D limits after a week in jumpspace.

 

[kaladorn]

I kinda like what Chris has suggested - that you can't jump towards any object (lower D) even if the net reduction exist. WRT any objects you are in the 'effect radii' of, you must jump in such a way as to increase your D. This suggests that the effects, though cumulative, are not additive - that is to say, you have to apply the effects of each object, but they aren't able to cancel one another out.

This means there might be no good course, though the one which is perpendicular to the line from one source to another would indeed be the only viable option (well, two options, since you have two directions). This might, OTOH, really limit *where* exactly you could jump to! (probably NOT another system).

I ask this for when I'm at one of the planets in side the 100D limit of the primary and I want to jump out or where the 100D limit of my planet might overlap the 100D limit of the primary (thus I can only get clear of both 100D limits by leaving the planet in direction *away* from the primary.

Now, seems to me a good way from a rules perspective to put a handle on this is to say you get jump modifiers for *each* object you are inside the 100D limit of.

In this case, that means you'd get a mod for being inside 100D of the planet and another for being inside 100D of the primary. That ought to make for a nice (bad) jump, hence you probably won't do it... unless you've got a Star-Destroyer-load of Imperial WhupAss(TM) about to be opened upon you, then it might make "sense" (I use the term loosely).

 

[kaladorn]

I can see from all this an interesting extension to the system generators would be a tool which could graphically (top down) represent the primary, any companions, all the planets and their orbits (or allowed drill down in the case you needed to see the satellites and their orbits).

And one option would be a 100D overlay for all system bodies.

And perhaps a calculation of course from location X (arbitrary) to a place outside of all 100D limits and the shortest time at varying G levels.

Of course, real sophistication would be to time index this info, then each time you return to the system, list the breakout time and hence generate the 'rotated' position of all the bodies.

If I was a happier graphics/UI programmer, I'd think about this.

 

[EvilDrGanymede]

Originally posted by kaladorn:
I can see from all this an interesting extension to the system generators would be a tool which could graphically (top down) represent the primary, any companions, all the planets and their orbits (or allowed drill down in the case you needed to see the satellites and their orbits).

And one option would be a 100D overlay for all system bodies.

Not quite what you asked for, but it's a start

http://members.shaw.ca/evildrganymede2/JTAS/solarsystem100D.gif

I whipped this up in POVRay - what you see there are the 100D limits for the bodies of our own solar system, to scale (1 pxl = 1.376 million km here). The white circles/dots are the 100D limits of the planets, not the planets themselves (you can't see the actual planets at this scale).

The big grey circle is the 100D limit of the sun, and the little yellow dot in the middle of it is the star itself. As you can see, it almost reaches Earth's orbit.

I couldn't put Pluto and Neptune on there without making everything else too small to be visible (or the image to be really huge!).

So as you can see, even the 100D limit of a big gas giant like Jupiter (which is at the high end of jovian diameters, and actually bigger than some brown dwarfs and comparable in size to late-M V stars) is pretty small on the scale of a solar system. Neptune would be about twice as far as Uranus is from Sol, and its 100D limit is about the same size. Pluto would be beyond that, but its 100D limit wouldn't even be visible on this scale.